The plugin tracks passing Minecraft in-game days from the moment the plugin is enabled. When you sleep or let the day pass by itself it keeps count and announces the count in chat to everyone.
Use the /setday <number> command to set it to any amount you like in case it needs to be updated. Need to be op to use.
You can get the current day from /time query day, unless if you have used /time set <amount> before, which will reset the query day command to whatever tick amount you chose, making it unreliable.
Nothing else, just a simple plugin I thought I needed.